Process of vulcanizing rubber and products obtained thereby



' introduced or incorporated in the rubber that- Patented a. 7,1930

UNITED STATES PATENT, oFncE 'SIDNEY M. CADWELL, OI LEON IA, NEW JERSEY, ASSIGNOR TO THE NAUGATUCKCHEMI- CAL COMPANY, A. CORPORATION 01 CONNECTICUT l v PROCESS OI VULCANIZING RUBBER AND PRODUCTS OBTAINED THEREBY 1N0 Drawing.

10 to eifect such compounding by milling which usually occurs at elevated temperatures. There are many substances which when incorporated with rubber at such elevated temperatures are themselves injuriously affected or affect the rubber injuriously. For example, combinations of highly reactive vulcanizing ingredients in sufiicient quantity to eflect vulcanization, which may injure the rubber by, causing it to burn on the mill.

In the present specification the broad term vulcanizing ingredient is applied both to a material which of itself can effect vulcanization and also to a material which in combination with other materials can assist in vulcanization fThe more specific term fvulcanizing agent is applied only to a material Y which of 1tself is capable of eifecting vulcanization. Accordingly the principal object of the 8 present invention are to provide a process which shall ermit the compounding of various vulcanizing ingredients with rubber without injury to themselves or to the rubber and to provide a series of rubber products therefrom having improved physical characteristics. t

l The invention broadly comprises a process of vulcanizing rubber in which a powerful combination of vulcanizin ingredients is so not more than a part of the entire combination is present in any onepo'rtion of rubber until the preliminary mixm and/or other operations have been substantially or entirely completed," then when desired completing the entirevulcanizing combination in the rubher, and vulcanizing. .It further comprises incorporating in abody of rubber a .part of "a powerful combination of vulcanizing in- 9 gredients, introducing the balance of the in- Application filed February'l, 1921. Serial No. 441,691.

gredients by diffusion ormigration, and vulcanizingl It further comprises impregnat ing a solid mass containing rubber with a non-gaseous halogen-free vulcanizin ingredient substantially without changing the form of the mass, and vulcanizing the rubber. It further comprises introducing parts of a powerful vulcanizing combination into different masses of rubber, sheeting out the masses of rubber, alternately plying the sheets, permitting the complete powerful vulcanizing combination to be formed through: out the plied up material by intermigratlon of ingredients between the plies, and vulcanizing;

In carrying out the invention in its preferred form 100 parts of rubber, 10 parts of zinc oxide, 6 parts of oxy normal butyl thiocarbonic acid disulphide and 3 parts of sulphur are compounded on the mixing mill. This stock may be designated as A. The oxy normal butyl thiocarbonic acid disulphide is' a liquid and constitutes a vulcanizing ingredient. Similarly another rubber compound may be mixed containing rubber 100 parts,

zinc oxide 10 parts, sulphur 3 parts, and aniline 4 parts. This compounded rubber may be designated as B. This compound will not vulcanize at moderateheat during a considerable period. Aniline is a liquid and constitutes another vulcanizing ingredient. Compounds A and B after being separately mixed with the vulcanizing ingredients as indicated are preferably blended in any desired manner as by passing through mixing rolls. 1 The blending, may be performed in any otherdesired manner than by.mixing rolls, fore-xam'plea hydraulic press may be used, or the two compounds may simply be laid on top of one another. The more intimate contact insures a more rapid absorption of the ingredients of compound A by com-pound B and vice versa. vAn article formed therefrom and allowed to stand for one week at 70 F. approximately (ordinary room temperature) is completely vulcanized, the vulcanizing ingredients ineach stock mutuallypermeating and impregnating the other stock. No heat is necessary for vulcanization although if heat is applied the vulcaniz'ation -is hastened. It is pointed out generally where heat is ap lied it is desirable to allow compounds, as and Bto stand about one day at ordinary temperature in order to allow lmpregnation of the vulcanizing ingredients throughout the stock before aplication of heat for vulcanization. It will he observed in the process just recited and those that follow that the formiven the rubber is substantially unchange by the process whereby permeation of the substances of compound A pass into those of compound B and vice versa. It will also be noted in the processes recited hereinafter that the form ofthe rubber whether as a sheet or in the form ofthread or other articles is substantalining a vulcanizing ingredient or ingredients which may-be milled at a high temperature and then treated with another vulcantially unchanged by the impregnating process. a

As a modification of the above procedure a rubber compound such as A having a thickness for example of .025 inches may be prepared and such material may then be allowed to stand in a room containing aniline fumes for approximately vulcanization is completed; or such compound may be-treated with liquid aniline for a day or so, enough aniline bein absorbed to cause the cure to become compete upon removal the efrom. Ifdesired a material such as ani ine may be employed to impregnate a fabric, the fabric being subsequently coated by calendering, for, example with the compound A. The combination of fabric and rubber upon standing for several days vulcanizes satisfactorily. I I

Another specific example ,of the process is as follows: 100 parts of rubber, 6 parts .of oxy ethyl thiocarbonic acid disulphide, 3 parts of sulphur and 10 parts zinc oxide are combined,

the oxy ethyl thiocarbonic acid disulphide constituting a solid vulcanizing in%edient, and a second compound is formed y com bining'lOO parts rubber, 4 parts aniline, 10 parts zinc oxide and 3 parts sul hur, the aniline in the latter compound orming a liquid vulcanizing ingredient. These compounds are alternately plied-in superposed sheets, pressed together and allowed to stand at room temperature at; approximately F. for 'one week, when vulcanization is complate. It will be understood that where the vulcanization temperature is higher a correspondingly shorter time is necessary forvulcanization. At 100 C. after standing for approximately a day as before pointed out, the

above masses react to vulcanize in approx mately 3Q .minutes. I

As another example of the process 100 parts of rubber,'2 parts of zinc oxide ,.2 parts of sulphur, and 4 parts of oxy normal butyl thiocarbonlc acid disulphide are mixed to form compound A. 100

zinc oxide, 2 parts of sulphur and 4 parts of aniline are mixed to form compound B.

These stocks are blended preferably as indifour days, whereupon parts of rubber, 2 parts cated above and if rolled out to form thin sheets .025 inches thick for thread stock, partial vulcanization, sufficient topermit handling of the material, may be secured in approximately two minutes at 275 F. Thereafter if such artially vulcanized materialbe placed in a c amber at -100 F. vulcanigation may be completed in approximately 1 ay. vulcanization is desired, the entire vulcanization, in the "present or the other examples, may be accomplished. athigh temperatures, that is, at normal hot vulcanizing temperatures from about 240 to 286 F. or even higher.

If it is desired to prepare a compound conizing ingredient, the following procedure may be carried out: parts rubber, 10 parts zinc oxide, 3 parts sulphur and 3 parts oxy It is obvious that if greater speedof normal butyl thiocarbonic acid disulphide.-

are combined by milling and calendering. The compound is then placed in a receptacle containing aniline fumes or such vulcanizing butyl thiocarbonic acid disulphide by dip ping or painting the latter material upon the article.

As a modification of 100 parts of rubber, 3 parts of Z1110 butylxanthogenate, 10 parts of zinc oxide and 3 parts of sulphur are compounded to form one rubber compound, and this material is then painted with aniline and allowed to stand .at approximately 70 F. whereupon vulcanization occurs shortly.

As another example of the process 100 arts rubber are combined with 3 parts zinc utyl xanthogenate and thoroughly mixed .to constitute one stock, 100 parts of rubber, 10 parts zinc oxide, 3 parts of sulphur and 4 parts para toluidine are combined to constitute a second compound. The first and second compounds are then applied to one another and on standing at approximately 70 F. vulcanied is treated" by suspension in ethyl amine gas at approximately 70 F. for one week at the end of which time vulcanization is found to be complete.

As another example of the process 100 parts rubber, 10 partszinc oxide 3 parts of sulphur and 3 parts of oxy ethyl thlocarbonic first with rubber and then treat an the above procedure I phide. This material after being compound- 1 acid disulphide are combined-and thereafter the rubber is suspended in ethyl amine gas at ordinary temperatures for one week at the end of which time vulcanization is com lete.

The specific examples given above in 'cate the use of sulphur, zinc oxide and an amine.

genate cures without the presence of zinc oxides; aniline and sulphur alone being able to efi'ect vulcanization in conjunction with the xanthogenate' Or the xanthogenate will vulcanize without the'addition ofan amine, zinc oxide and sulphur being alone employed.

Among other materials which may be employed in carrying out the process herein indicated replacm materials herein noted are the followin n the class of thiocarbonic acid dlSlllPhldBS may be mentioned the oxyethyl, ox'ybutyl, oxyamyl, oxymethyl compounds and the anal ous compounds acetyldisulphide, benzoyl isulphide, and dithiobenzoyldisulphide. In t e class of xanthogenates may be mentioned the mercuric ethyl, potassium am 1, zinc amyl, copper ethyl, zinc ethyl, barium eth 1, sodium methyl, lead methyl, zinc metyl, lit ium ethyl, magnesium I ethyl, calcium ethyl, potassium butyl, zinc but 1, potassium ethyl, sodium ethyl, and lea ethyl compounds. The reactions of these compounds will naturally vary according to the nature of the substituted group and metal, both in the speed of vulcanization and in the physical properties of thefvulcanizate. v

Oxy normal butyl thiocarbonic acid disulphide is both an accelerator and a vulcanizing agent as distinguished from' an accelerator only and when present in sufiicient amounts will cure without sulphur. It has been found to cure without the addition of an amine. In general where an agent of this type is capable of .vulcanizing rubber unaided when present in sufficient quantity it will be observed that; the proportions should be so adjusted that the rate of vulcanization is sufficiently slow to avoid prevulcanization or burning upon com oundin but the proportions bein such t at rapid vulcanization will occur w en another cooperating vulcanizing ingredient is thereafter applied.- The presence of zinc oxide in. rubber'stocks is not necessary on all occasions, but a zinc compound is present when mater als of the class of oxy normal butyl thiocarbonic acid disul hide are used. Generally better results are 0 tained when zinc oxide is included in the compounded stock. A transparent stock may be obtained by reducing the amount of zinc oxide to 0.5%.

It will be observed that in general the materials such as oxy normal butyl thiocarbonic acid disulphide and zinc butylxanthogenate mentioned herein are derivatives of carbon ess are found to possess in general desirable physical properties. The process is simple and effective and avoids the use of expensive apparatus, permit-s the use of highly active vulcanizing combinations'and in general ac-' j complishes the objects herein-above set forth. It is particularly pointed out that vulcanization at low temperatures according to the process herein possesses advantages over low temperature processes heretofore known such as sulphur monochloride vulcanization, in that the present process permits accurate control of the degree of vulca'nization' and hence of the ph sical properties of the resulting vulcanize rubber. It is also particularly true that ageing of the products of the present process is superior to ageing of the products of the sulphur monochloride cure. Further dyestuffs and fibrous materials such as cotton may be employed without injury in the present process, whereas such use has been prohibited in sulphur monochloride vulcanization. I

As many apparently widely different embodiments of this invention could be made without departing fromthe spirit thereof, for instance, it is clear that where the supplementary vulcanizing ingredient is applied to the surface of the rubber stock, heat may be used at the same time to hasten absorption .into the rubber stock and/or to quicken vulcanization, and it will be understood that I do not intend to limitm self to the specific embodiment herein set orth except as indicated in the appended claims.

Having thus described my invention, what I claim and desire to protect by Letters Patent is: i

1. A process of treating rubber which comprises impregnating a mass containing rubv er with a non-gaseous halogen-free vulcan- 'hot vulcanizing temperatures. 1 1 3. A process for treating rubber which comprises impregnating a mass containing rubber and an organic sulphur containing vulcanizing ingredient with another cooperating vulcanizing ingredient, substantially I vulcanizing the rubbe without changing the form of themass, and

4. A process of vulcanizing rubber which comprises combining with a mass of rubber gredients, and subjecting the I ing ingredients,

' erator substantially a vulcanizing in redient, combining with a second mass of ru ber another vulcanizing inredient, associating the separately comined masses of rubber andvulcanizing insame to a suitable temperature for a suficient length of timeto efiect vulcanization. v

5. A process of treating rubber which comprises combining with rubber oxy norymal butylthiocarbonic acid disulphide, and

treating the com ound with an amine adapted, to permeate t e rubber.

8. The process of making rubber articles comprising bringing into intimate contact bodies of rubbercontaining respectively oxy normal butyl thiocarbonic acid disulphide,

zinc oxide, and sulphur, and paratoluidine, zinc oxide and sulphur, and allowing vulcanization to proceed.

v 9. A step in a process of vulcanizing rubberwhich comprises impregnating a mass containing rubber with a non-gaseous vulcanizing compound, substantially without changing the form of the mass, at a temperature below 100 C.

10. A step in a process of treating rubber which comprises impregnating a mass con-.

taining rubber with a low temperature accelwithout changing the form of the mass.

11. Astep in a process of vulcanizing rubber which comprises impregnating a mass containing rubber witha halogen-free liquid vulcanizing ingredient at a temperature becontaining vulcanizing v 12. A step in a process of vulcanizing rubher which comprises impregnating a mass containing rubber ingredient with another vulcanizing ingredient, substantially without changingthe form of the mass.

- 13. A step in the process of vulcanizing rubber consisting in allowing oxy norm butyl thiocarbomc ac d disulphide and. aratoluidine to interact inthe presence 0 .rub-

her.

article containing a vulcanizing and an organic sulphur 14. The process of making a rubber arti-,

cle comprising calendering to a fabric a sheet of rubber containing zinc oxide, sulphurand oxy normal butyl thiocarbonic acid sulphide, applyingto the rubber another sheet of rubber containing sulphur, zinc oxide and paratoluidine, and continuing the building up of such alternate plies to complete the'article.

15. As a new product a vulcanized rubber produced ,from rubber anda vulcanizing ingredient, impregnated with a second vulcanizing ingredient, substantially without changing the form ofthe mass, sa1d ingredients including an organic accelerator.

16. A process comprises impregnating a mass containing rubber and an organic sulphur containing vulcanizing ingredient with an accelerator, substantially .without the mass, and vulcanizing therubber.

17. A process comprises impregnating a mass containing rubber and an organic sulphur containing vulcanizing ingredient with an amine, substantially without changing mass, and vulcanizing the rubber.

- 18. A process of treating rubber which comprises impregnating a mass containing rubber with a non-gaseous halogen-free vulcanizing compound, substantially without changingthe form of the mass, and vulcanizing the rubber at a tempgrature below 100 C. y

19. Aprocess for treating rubber which comprises impregnating a mass containing rubber and an organic sulphur containing vulcanizing ingredient with an accelerator, substantially without changing the form of the mass, and. vulcanizing the rubber at a temperature below 100 C.

20. A process for treating rubber which comprises impregnating a fabricated rubber ingredient with a second vulcanizing ingredient, said ingredients including an organic accelerator substantially without changing the form of the article, and vulcanizing'the article.

21. A process for treatin rubber which comprises impregnating a fa ricated rubber article containing an organic sulphur containing vulcanizing agent with an amine substantially without changing the form of the for treating rubber which changing the form of for treating rubber which the form of the taining sulphur and an adjoining ply an accelerator.

24-. The herein described method of forming a sheet or slab of rubber which comprises superpo'sing one upon the'other a plurality of plies of rubber com ound,one-ply containing sulphur and t e other an accelerator, and thereafter raising the temperature of the superim osed lies.

25. The hereln described method of forming a rubber article which comprises superposing uponeach other a plurality of plies to'secure the required thickness, said plies containing alternately sulphur and an accelerator. I o 26.- The herein described method of forming a vulcanized rubber compound which comprises bringing together a plurality of plies of rubber, adjoining-plies containing respectively ingredients which are migratory under moderate heat but which plies are ino. dividually non-vulcanizable under such modcrate heat, and thereafter raising the temper-' ature of the adjoined plies to eifect migration of the ingredients and vulcanization of the article. 7 I v k 27. The herein described method of forming a vulcanized rubber sheet or slab which comprises mixing separate batches of rubber .compound, .one batch containing sulphur and another batch an accelerator, separately calendering said batchesinto sheets and thereafter superposing said sheets and,vulcanizing them together. 7 28. A process of treating rubber which comprises combining in at least two superposedlayers of rubber, materials comprising sulphur, a mi ratory organic accelerator,

' and metal in com ination, at least two of the materials being combined with one of said layers of rubber, and subjecting to a vulcanizing temperature.

.29. A process of treating rubber which comprises combining in at least two superposed layers of rubber, materials comprising sulphur, a migratory vulcanization accelerator which is a derivative of carbon disulphide, and zinc in combination, at least two of the materials being combined'with one of l tosaid layers of rubber, and-subjecting to a suitable vulcanizin temperature.

30.Aprocess o treating rubber which comprises combining in at least two superposed layers of rubber, materials comprising.

sulphur, a migratory vulcanization accelerator which is a derlvatlve of carbon disulphide, zinc in combmatlon, and an amine, at

east twov of the materials;being combined with one of saidlayers of rubber, and subjecting. to a" suitab ture.

315A process of treating rubber which "comprises disposing in desired form a body of rubber containing part of a powerful vul- "canizingcombination which includes an ore vulcanizing temperaganic accelerator and introducing the bah ance of said combination by difiusion.

32. A process of treating comprises aggregating in desired form a body of rubber and vulcanizing said body by the difiusion therein of complementary low temperature vulcanizlng an organlc accelerator.

33. A process of treating rubber which comprises aggregating in desired form a,

body of rubber and vulcanizing said body by combining therein com lementary vulcanizing ingredientsby di usion, saidingredients including an organic accelerator.

34. A process of producing vulcanized rubber which comprises introducing into rubber vulcanizing ingredients including sulphur, metal in combination, and an organic accelerator, forming the rubber stock as desired,

and vulcanizing the stock while applying to the surface thereof amigratory ingredient adapted to supplement the vulcanizing action of the ingredients contained in the stock,

35. A process of producing vulcanized rubher, which comprises preparing a stock containing rubber and some but less than the rubber ,which:

ingredients including total ingredients of vulcanization, 'forming as desired, and vulcanizing in a medium contaming an ingredlent'ofvulcanization complementary to'the lngredlents of vulcanization in said'stock, said total ingredients ineluding an organic accelerator.

36. A process of forming a sheet or slab of( rubber which comprises superposing one upon the other a plurality of plies of rubber compound, one ply containing sulphur and an adjoining ply an accelerator, causing sul phur to migrate into the ply containing the accelerator, and 'vulcanizmg said last mentioned ply.

of. a low temperature vulcanizing combinalayer the balance of .tion and an ad'oinin J subjecting to asuitsaid combination an able vulcanizing temperature.-

39. A. process of producing vulcanized rubber which comprises preparing a stock containing rubber and less than the total ingredients adapted to form a low temperature vulcanizing combination which includes an organic accelerator,fforming as desired, and vulcanizing said -stock by the diffusion therein of the balance of said low temperature vulcanizingiiigredients.

40. Process of producing vulcanized rubber which comprises incorporating with rubber less than the total of desired ingredients of vulcanization but including an organic accelerator, forming as desired, causing. to inigrate into the stock the balance of said ingredients of vulcanization and vulcanizing the rubber.

41. Process of forming a sheet orslab of rubber which comprises superposing one upon the other plies of rubber compound, one ply containinga migratory accelerator and; an adjoining ply containing sulphur but not said accelerator, and vulcanizing.

42. A process of producing vulcanizedrubher which comprises incorporating'with rub ber vulcanizing ingredients including sulphur, organic accelerator and metal in combination, forming as des1red,-and vulcanizing adapted to coact with the ingre ients in the stock to supplement their vulcanizing action.

44. Process of producing vulcanized-rubber which comprises introducing vinto rubber, vulcanizing ingredients including sulphur, metal in combination, and an organic accelerator, shaping the rubber stock into dethereof sired form, applying to the surface a migratory vulcanizing ingredient in gaseous form and subjecting the stock to a suitable temperature fora suflicientflength of time to effect vulcanization.

' 5; The herein described method of form-' ing a sheet or slab of rubber which comprises superposing one upon the other a plurality of plies of rubber "compound, one ply-containing sulphur and zinc oxide and an adjoiningply an accelerator in the presence ofzinc ox de.

46. The hereinbefore described method of effecting the vulcanization of rubber compounds which comprises incorporating with the rubber compound one of two ingredients which will coact to effect vulcanization, ap-

plying the other ingredient to'the surface of the rubber compound, one of said ingredients being organic,'and thereafter causing I the surface ingredient to penetrate the rubthe rubber compound one of two ingredients,

her and coact with the first named ingredi-. ent to efiect vulcanization.

47. The hereinbefore described method of effecting the. vulcanization of rubber com- 55, A process of preparing compositions pounds which comprises incorporating with which will coact to effect low temperature ing the vulcanization ing the rubber in separate batc es,

vulcanization, applying the other ingredient to the surface of the rubber compound, and thereafter'heating the rubber compound to cause the surface ingredient to flow and penetrate the rubber compounds.

48. The'hereinbefore describedmethod of effecting the vulcanization of rubber compounds which comprises incorporating with the rubber compound one of two ingredients which will coact to effect low temperature vulcanization, mixin the other ingredient with a suitable carrier and applying it to the surface of the rubber com ound, and thereafter heating the compoun 49. A process of treating rubber which com rises introducing into rubber vulcanizing ingredients including sulphur; a vulcanization accelerator which is a derivative of carbon disulphide, metal in combination, and an amine, at least one of the named materials being introduced by diffusion, and vulcanizingthe rubber.

50. A process of producing vulcanized rubber which comprises incorporating with rub ber, vulcanizing ingredients including sulphur, organic accelerator, and zinc in combination, forming as desired, applying to the surface of the stock a mi ratory vulcanizing ingredient adapted to quicken the vulcanization of the rubber and subjecting to a suitable vulcanizing temperature. a a

51. The herein described method of effectof rubber compounds which comprises incorporating with the Y compound a suitable applying to the exterior thereof an organic accelerator, and causing the accelerator to penetrate the compound.

52. The herein described method of effecting the vulcanization of rubber compounds which comprises incorporating withthe compound a suitable proportion of sulphur, applying to the exterior thereof an organic accelerator, and heating the compound to cause the accelerator to'penetrate the compound.

53. A process ofpre aring compositions containing a vulcanizab e plastic material, a vulcanizing agent, and anaccelerator of vulcanization which comprises .mixin the composition in separate batches with t e vulcanizing agent and accelerator incorporated reproportion ofv sulphur,

spectively in different batches, and combining the batches just prior to using the same. 54.'A process of pre arin compositions containing a vulcaniza le p astic material,

,a vulcanizing agent, and an accelerator of vulcanization which comprises mixing the composition in separate p astic batches, one of which contains the vulcaniz' ng a cut but does not contain the accelerator, an mixing the batches just prior to using the same.

one of which contains the sulphur but not the accelerator and the other of which contains the accelerator but not the sulphur, and mixing the batches just prior to using the same.

56. A process of producing vulcanized rubber composition which comprises forming separate batches of rubber composition, each batch containing relative to the other complementary low temperature Vulcanizing ingredients, combining the batches when desired whereby there may he formed a complete low temperature vulcanizing combination and subjecting the combined batches to a vulcanizing temperature.

- 57. A process'of preparing plastic compositions which will cure at relatively low temperatures which comprises milling a composition which may be vulcanized only at a high temperature until the plastic component thereof is broken down and combinlng therewith a non-v'ulcanizable plastic composition containing a vulcanization accelerator of the carbon bisulphide addition-product series.

' 58. The process of preparing low-temperature-curing compositions containing a plas- I tic material which comprises combining a milled mixture containing a vulcanizing agent and a. part of the plastic material, but not containing a vulcanization accelerator, with a non-vulcanizable milled-mixture containing plastic material and an accelerator of vulcanization.

59. A process of preparing vulcanizabl-e compositions which comprises milling the composition in separate batches with sulphur and an accelerator of vulcanization respectively incorporated indifferent batches, and milling the batches together ;atv.,a lower-;temperature thanis generated duringtheaniH- ing of the separate batches.

Signed at- New York, New York; this 28th day of January, 1921.

- SIDNEY M. CADWELL. 

